fix(platform): properly join URL paths in HttpClientRequest.appendUrl

[codewithkenzo]

Summary

Fixes HttpClientRequest.appendUrl to properly join URL paths instead of using simple string concatenation.

Closes #5971

Problem

The current implementation could produce invalid URLs:

// Before (broken):
HttpClientRequest.get("https://api.example.com/v1").pipe(
  HttpClientRequest.appendUrl("users")
)
// Result: "https://api.example.com/v1users" (missing slash!)

Solution

Ensure proper path joining by:

1. Adding a trailing slash to base URL if missing
2. Removing leading slash from path if present

// After (fixed):
HttpClientRequest.get("https://api.example.com/v1").pipe(
  HttpClientRequest.appendUrl("users")
)
// Result: "https://api.example.com/v1/users"

This matches the behavior of other HTTP client libraries like axios, got, and ky.

Test Cases

Base URL	Path	Result
https://api.com/v1	users	https://api.com/v1/users
https://api.com/v1/	users	https://api.com/v1/users
https://api.com/v1	/users	https://api.com/v1/users
https://api.com/v1/	/users	https://api.com/v1/users

Verification

• Type check passes (pnpm check)
• All tests pass (18/18 in HttpClient.test.ts)
• Changeset added

[changeset-bot]

🦋 Changeset detected

Latest commit: 784721d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 31 packages

Name	Type
@effect/platform	Patch
@effect/cli	Patch
@effect/cluster	Patch
@effect/experimental	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/rpc	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-drizzle	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-node	Patch
@effect/sql	Patch
@effect/workflow	Patch
@effect/ai	Patch
@effect/ai-amazon-bedrock	Patch
@effect/ai-anthropic	Patch
@effect/ai-google	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/sql-kysely	Patch

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[codewithkenzo]

This implements the fix discussed in #5971 - using smart path joining to ensure a slash exists between base URL and appended path, while preserving the "append" semantics (paths starting with / are still appended, not treated as absolute).

Happy to adjust the approach if you'd prefer full URL spec compliance via new URL() instead.

[tim-smart]

Suggested change

	strictEqual(request.url, "https://api.example.com/v1/")
	strictEqual(request.url, "https://api.example.com/v1")

[codewithkenzo]

Nice catch, updated so empty path returns the request unchanged, thank you!